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Pharmacological prevention of serious anaphylactic reactions due to iodinated contrast media: systematic review

Created: 1/2/2007


Pharmacological prevention of serious anaphylactic reactions due to iodinated contrast media: systematic review

Tramer MR, von Elm E, Loubeyre P, Hauser C.

BMJ. 2006 Sep 30;333(7570):675.


  • Each year, about 60 million doses of iodinated contrast media are used worldwide.
  • Iodinated contrast media can cause severe anaphylactoid reactions
  • Despite the fact that the increased use of non-ionic iodinated contrast media has been associated with a decrease in the incidence of mild to moderate, and possibly severe, reactions, prophylactic drug regimens that aim to decrease the incidence of reactions (premedication) are still widely used in clinical practice
  • A variety of premedication regimes in patients with a previous reaction to high osmolality iodinated contrast media exist.
  • These include combinations of methylprednisolone with or without an antihistamine, oral prednisolone or methylprednisolone, or intravenous hydrocortisone and intramuscular diphenhydramine
  • Considerable variation exists in recommended pretreatment regimens and they are based on observational data
  • The current study aims to review the efficacy of pharmacological prevention of serious, potentially life threatening reactions to iodinated contrast media

Data sources

  • Systematic search (multiple databases, bibliographies, all languages, to October 2005) for randomised comparisons of pretreatment with placebo or no treatment (control) in patients receiving iodinated contrast media.


  • Nine trials (1975-96, 10 011 adults) tested H1 antihistamines, corticosteroids, and an H1-H2 combination
  • No trial included exclusively patients with a history of allergic reactions
  • Many outcomes were not allergy related, and only a few were potentially life threatening
  • No reports on death, cardiopulmonary resuscitation, irreversible neurological deficit, or prolonged hospital stays were found
  • In two trials, 3/778 (0.4%) patients who received oral methylprednisolone 2x32 mg or intravenous prednisolone 250 mg had laryngeal oedema compared with 11/769 (1.4%) controls (odds ratio 0.31, 95% confidence interval 0.11 to 0.88)
  • In two trials, 7/3093 (0.2%) patients who received oral methylprednisolone 2x32 mg had a composite outcome (including shock, bronchospasm, and laryngospasm) compared with 20/2178 (0.9%) controls (odds ratio 0.28, 0.13 to 0.60)
  • In one trial, 1/196 (0.5%) patients who received intravenous clemastine 0.03 mg/kg and cimetidine 2-5 mg/kg had angio-oedema compared with 8/194 (4.1%) controls (odds ratio 0.20, 0.05 to 0.76)


  • The existing evidence suggests that a large number of unselected patients need to receive an oral double dose of methylprednisolone to prevent a potentially life threatening, iodinated contrast medium related reaction in one of them
  • For antihistamines, limited evidence shows that they may prevent some reactions
  • Valid data supporting the efficacy of drug combinations or the use of premedication in patients with a history of allergic reactions are completely lacking
  • Severe allergic reactions due to contrast media seem to be rare; this may explain why no reports of disastrous reactions exist
  • Allergologic evaluation including cutaneous tests and biological assessment to identify and eliminate the culpable agent has been proposed in all patients with a history of an anaphylactic reaction to a contrast medium. However, only a fraction of patients with severe and life threatening reactions have a positive skin test for the administered contrast material.
  • Another approach would be to train physicians who are using iodinated contrast media to recognise and treat anaphylactic reactions appropriately
  • Accordingly, radiology departments should be staffed with the necessary equipment for resuscitation.
  • Physicians dealing with patients receiving contrast media should not rely on the efficacy of premedication; routine prophylaxis should be abandoned

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